Development of clinical applications of RNAi therapy has been hampered by a number of hurdles. The most difficult roadblock has been achieving safe, effective delivery of siRNA to specific target cell types or tissues. We thus seek to develop reliable technology for oral siRNA delivery, with the goal of applying it as rapidly as possible to therapies which will have maximal impact on human health. RNAi-based therapies targeting macrophages could transform the practice of medicine for numerous major human diseases including type 1 and 2 diabetes, atherosclerosis, arthritis and inflammatory bowel disease. We have previously described a novel siRNA delivery system based on 21,3-D-Glucan-encapsulated siRNA Particles (GeRPs) as efficient oral delivery vehicles that potently silence genes in mouse macrophages in vitro and in vivo. We propose to develop this technology as a novel therapeutic approach for these and other diseases. We propose to quantitate and optimize the delivery of siRNA encapsulated within GeRPs to macrophages in multiple tissues. We will also improve GeRP formulations to maximize potency and duration of target gene silencing. Finally, we will test the ability of GeRP-mediated gene silencing in inflammatory macrophages to ameliorate disease in mouse models of insulin resistance and type 2 diabetes. These will be critical steps toward developing clinical therapies based on RNAi-mediated gene silencing in macrophages. The impact of developing a vehicle for orally delivering siRNA to macrophages in humans would be potentially huge given the large number of major diseases that could be targeted.